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  • VDB export not loading in Blender/Tyflow correctly

    I've read hours about VDB and what it is and how it works today and I'm still stuck.
    Software: Max 2022.3 Phoenix 4.40 Blender 3.0 Tyflow v0.16133

    I simulated a simple sphere burning with temp, smoke, velocity and uvw channels. The first round I did it with setting to vdb drop down. Then I made a version with .aur and used the cache_converter just in case something gets scrambled.
    The VDB made in phoenix loads properly in a vrayvolumegrid. It also plays back correctly in Phoenix and it renders correctly in Vray.

    If I load the VDB in Tyflow and vdb to mesh = only a few really low rez clusters even though I set my iso lines and voxel levels to super high details.
    If I load the VDB in Blender, and then apply a vdb to mesh modifier, it only gives me a solid cube the size of the domain so either its not reading the density right or something isn't translating with the grids.
    So I then tested if its the vdb I made or just vdb in general.

    I downloaded an animated vdb from Embergen and a still VDB from Openvdb website and both of them load in Tyflow and Blender correctly without doing much.
    The tutorials I see online to convert phoenix aur to vdb were easy, so that part is no problem. The tutorials I see online for Phoenix to Blender show its just plug and play and works as it should without changing grid names, temperature ranges etc.

    Anyone else running into an issue? I've tried keeping scale the same units, exporting with all grid channels and trying to load each one separate as the density and nothing working as easy as the tutorials online I see. I have a 60 mb zip of 3 vdb files I can send. The embergen, the openvdb and the one I simmed, but its too big for posting.

    Thanks for looking!

  • #2
    Hey,

    The Phoenix vdbs use different names for the grid channels compared to the caches from the OpenVDB website or other software. This is why you will need to tell tyFlow and Blender to use these specific channels instead of searching for the default ones.
    I don't have Blender installed, but here is how it goes in tyFlow ( the process should be similar in Blender).

    Once you load your vdb sequence in tyFlow you need to disable the checkbox for Automatic grid extraction. Then you can press the Extract grid names button and it will show you how the grid channels are named.
    Then it is a matter of setting up the channel you wish to use for the density - in my case I chose Temperature_phx.

    Note that different grid channels will have different ranges ( this is really important for the meshing step). You can find more about the grid channel ranges here - https://docs.chaos.com/display/PHX4M...Channel+Ranges
    After that you just need to set the VDB to Mesh operator to use Density an input and dial in the Iso value - in this case for the temperature I chose 800 and got the result as in the attached screenshot.

    Hope this helps.
    Attached Files
    Georgi Zhekov
    Phoenix Product Manager
    Chaos

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    • #3
      georgi.zhekov yeah I did do that part for sure, replacing the density grid with temperature_phx, I tried fuel_phx, smoke_phx etc. I think the next attempt will be the ranges. Thats the only thing I haven't touched yet. The final clue I believe in is the rollout for the vdb to mesh operator. I didn't go high enough. Will try that first and see results. Thanks for feedback.

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      • #4
        georgi.zhekov Yup it was the iso value wasn't high enough. Thanks again.

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